the effect of the greenland ice sheet melting on global warming

8/9/2019 The Effect of the Greenland Ice Sheet Melting on Global Warming

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Introduction:

The Greenland ice sheet is more than 100,000 years old. Scientists core through

four kilometers of ice to study proxies for climate. However, the importance of the

Greenland ice sheet stretches beyond scientific information. The Greenland ice sheet is the

second largest body of ice in the world after the Antarctic ice sheet. Ice sheets provide

95100% of global albedo, making the Greenland ice sheet an important impactor to solar

radiation (Than 2012). Greenhouse gases are also being increased, much of which is

attributed to human interaction. In 2012 melting on the Greenland ice sheet jumped from

40% of sheet surface melt on July 8th to 97% sheet surface melt four days later (see

fig.1) (Than 2012). The melting of the Greenland ice sheet will decrease global albedo,

increase sea level, and possible affect the North Atlantic conveyor belt.

Discussion:

The international Greenland Ice Sheet Monitoring Network (GLISN) lists 33

research stations with the common goal of monitoring the Greenland ice sheet.

Measurements of the Greenland ice sheet melting began in 1979 and by 2002 melting

had increased by 16% (Howat et. al 2013). Over the pastforty years, satellite images

show that meltwater lakes have significantly advanced. Enhanced melt water effect is

when glacial melt onto of the ice sheet is funneled through moulins and reaches the

glacial base (although some moulins drain into the ocean, not the glacial base). As the

water builds up, it forms a barrier between the ice sheet and the glacial base and acts as a

lubricant. This not only leads to an increase in melt, but it also allows for the ice sheet to

slide. The increase of the meltwater lakes and as well as the equilibrium line moving


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farther up the ice sheet shows no limit for meltwater expansion (Howat et. al 2013).

Once ice sheet begins, it forms a positive feedback loop and the melting accelerates

to an exponential and erratic pace. At a station in Greenland called Swiss Camp in 2005,

scientists discovered through GPS readings that during melting, the ice sheet didnt shrink

in size, but instead was sliding from its foundation. From 1996, the readings were

movement rate of 13 inches a day, to in 2001 when movement rate was 20 inches a day

(Kolbert 2006). Further melting of the Greenland ice sheet is enhanced by the surface

meltwater sinking to the bed of the ice, creating a cushion between the bedrock and the

ice sheet, accelerating the melting as well as the ice sheet slip. At the end of the last glacial

period, much of the Northern Hemispheres glaciers receded in just a few thousand years,

even though it took many thousands of years for them to grow to their maximum size.

This suggests that when an ice sheet melts, flow rates increase, which increases thinning

and perpetuates the cycle (Kolbert 2006).

As stated in the introduction, the Greenland ice sheet has dramatically increased

since then. In fact, the ice sheet melt had a melting breaking year in 2010, only to be

broken in 2012. In a period of four days in July 2012, the percentage of melt went from

40% to 97%, shown in the figure below. Left shows July 8th, with July 12th shown at the

right. The red shows melt on the Greenland ice sheet during those times.


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http://news.nationalgeographic.com/news/2012/07/120725greenlandicesheetmeltsatellitesnasaspacescie

nce/

Many factors contribute to the rapidity of the Greenland ice sheet melting. Two of

the main causes of the increased melting are; enhanced meltwater effect and force

imbalance. This leads to the second main cause, because there is now an imbalance of

forces on the ice sheet. This causes the line of equilibrium to be raised, and the ice sheet

begins to break and crack (Fettweis et. al 2013).

Increased precipitation is another factor in the imbalance of forces on the

Greenland ice sheet. As the climate warm, snow accumulation in Greenland increases. The

accumulation of snow at the top of the ice sheet, along with the glacial runoff flowing to

the glacial base makes the ice sheet top heavy. This also leads to a positive feedback loop

and perpetuates the cycle of melt (Rae et. al 2012). Because the ice sheet is now top
http://www.google.com/url?q=http%3A%2F%2Fnews.nationalgeographic.com%2Fnews%2F2012%2F07%2F120725-greenland-ice-sheet-melt-satellites-nasa-space-science%2F&sa=D&sntz=1&usg=AFQjCNHwFqtZ233ZGa5AZSBvBM_cFxNONAhttp://www.google.com/url?q=http%3A%2F%2Fnews.nationalgeographic.com%2Fnews%2F2012%2F07%2F120725-greenland-ice-sheet-melt-satellites-nasa-space-science%2F&sa=D&sntz=1&usg=AFQjCNHwFqtZ233ZGa5AZSBvBM_cFxNONA


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heavy, it becomes unbalanced and it begins to crack. The cracking ice is less stable and it

can break off into the ocean, increasing melt and perpetuating the cycle.

What does this mean for the Earth? The most dramatic consequence of the melting

Greenland ice is raising sea levels. During the previous interglacial called the Eemian,

evidence shows that sea levels were as much as 15 feet higher than present day (Kolbert

2006). Two major theories name different ice sheets responsible for the higher Eemian

sea level: one claims it was meltwater from Greenland, another states it was the collapse of

the West Antarctic ice sheet. Both theories agree that melting ice sheets are responsible

for the high sea level (Kolbert 2006). If the entire Greenland ice sheet were to melt,

scientists project that sea level would rise seven meters (Wilton 2013).

If the Greenland ice sheet were to melt, not only would the sea level rise, but global

albedo would decrease. Albedo regards the reflectivity of an object. If an object reflects

the suns rays, it will have a high albedo rating and the number will be closer to 1. If it has

low albedo, the rating will be closer to 0. The albedo of The Greenland ice sheet is .91,

meaning it reflects most of the suns rays (Wilton 2013). If the Greenland ice sheet were

to melt, then instead of the highly reflective ice, there would be exposed earth and ocean,

which absorbs the suns rays. Instead of the suns energy being reflected back into the

space, it would stay in the Earth, and lead to further climate warming.

The glacial meltwater that could cause sea level rise could also cause the

thermohaline circulation to shut down. Thermohaline circulation is the circulation in

which the ocean transfers warm and cold water. If an abundance of fresh water were to

be introduced to the ocean, that would cause the salt water to sink to the bottom of the


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ocean. As the Greenland ice sheet is melting at exponential levels, more and more fresh

water is being leaked into the ocean. Because of the Greenland ice sheet melt water going

into the ocean, the thermohaline conveyor could be dampened. This would slow down the

circulation of warm and cold water, as well as the air it carries. A negative feedback loop

can be made from this scenario, and instead of the climate continuing to warm and the

Greenland ice sheet increasing in melt percentage, these events could be dampened (Rae

et. al 2012).

Conclusion:

Further research needs to be done in order to find out the extent humans have

caused the melting of the Greenland ice sheet and most importantly, what can be done to

save the Greenlands ice sheet. As pointed out in the hockey stick controversy (see fig. 2),

most of the climate that we live in today accelerated during the Industrial Revolution. By

the time the majority of the public realizes that losing Greenlands ice sheet is detrimental

to Earths climate, it will be too late to undo the damage. The outcome of the Greenland ice

sheet melting will be reinforced and empowered because many of the effects form

positive feedback loops. Many positive feedback loops also trigger other climate events,

which start of more positive feedback loops to global warming.


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http://ossfoundation.us/projects/environment/globalwarming/myths/thehockeystick

References Cited:

Box, J. E., Cappelen, J., Chen, C., Decker, D., Fettweis X., Mote, T., Tedesco, M., van de Wal,

R.S.W., Wahl, J., 2013 Greenland Ice Sheet: NOAA.http://www.arctic.noaa.gov/reportcard/greenland_ice_sheet.html (accessed November

2013)

Fettweis, X., Franco, B., Tedesco, M., Van Angelen J. H., Lenaerts J. T. M., Van Den Broeke M.

R., Galle H., 2013 Holocene thinning of the Greenland ice sheet: Cryosphere, v. 7 Issue 2, p

469489

Howat, I. M.; S. de la Pea; van Angelen, J. H.; Lenaerts, J. T. M.; van den Broeke, M. R.

Expansion of meltwater lakes on the Greenland Ice Sheet Cryosphere. 2013, Vol. 7 Issue 1,p201204. 4p.

Kolbert, E. 2006 Field Notes From a Catastrophe Man, Nature, and Climate Change

Rae, J. G. L.; Aalgeirsdttir, G.; Edwards, T. L.; Fettweis, X.; Gregory, J. M.; Hewitt, H. T.; Lowe,

J. A.; LucasPicher, P.; Mottram, R. H.; Payne, A. J.; Ridley, J. K.; Shannon, S. R.; van de Berg,

W. J.; van de Wal, R. S. W.; van den Broeke, M. R. 2012. Greenland ice sheet surface mass

balance: evaluating simulations and making projections with regional climate models:

Cryosphere. Vol. 6 Issue 6, p12751294

Than, K., 2012. "Shocking" Greenland Ice Melt: Global Warming or Just Heat Wave?:

National Geographic.

http://news.nationalgeographic.com/news/2012/07/120725greenlandicesheetmelts

atellitesnasaspacescience/ (accessed November 2013)

Wilton, M., 2013. Sea IceAlbedo Feedback and NonLinear Arctic Climate Change:

NOAAhttp://www.gfdl.noaa.gov/bibliography/related_files/mw0901.pdf (accessed

November 2013)
http://www.google.com/url?q=http%3A%2F%2Fnews.nationalgeographic.com%2Fnews%2F2012%2F07%2F120725-greenland-ice-sheet-melt-satellites-nasa-space-science%2F&sa=D&sntz=1&usg=AFQjCNHwFqtZ233ZGa5AZSBvBM_cFxNONAhttp://www.google.com/url?q=http%3A%2F%2Fwww.gfdl.noaa.gov%2Fbibliography%2Frelated_files%2Fmw0901.pdf&sa=D&sntz=1&usg=AFQjCNFHUqi3E7hAyVwu_VN5EIqyBLSZdwhttp://www.google.com/url?q=http%3A%2F%2Fwww.arctic.noaa.gov%2Freportcard%2Fgreenland_ice_sheet.html&sa=D&sntz=1&usg=AFQjCNHAoB5FuH-NuUxvlF8GxhBGMv8WHghttp://www.google.com/url?q=http%3A%2F%2Fnews.nationalgeographic.com%2Fnews%2F2012%2F07%2F120725-greenland-ice-sheet-melt-satellites-nasa-space-science%2F&sa=D&sntz=1&usg=AFQjCNHwFqtZ233ZGa5AZSBvBM_cFxNONA

the effect of the greenland ice sheet melting on global warming

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